Piston ring and method of making same



v w. H. FARR Nov; 14, 1944. PISTON RIfiq AND'METHOD OF MAKING S'AME'V Filed Ndv. 16, 193s -INVENTOR: WZzrren/ HJ'arr ATTORNEY.

Patented Nov. 14, 1944 PISTON RING Warren H. Fa.rr, Detroit, Mich, assignor to Budd Wheel Company, Philadelphia, 2a., a corporation of Pennsylvania Application November 1c, 1938. Serial No. 240,676 4 Claims. (c1. 399-44) The present invention relates in general to resilient bearing elements and method of makin the same, and more specifically to metallic piston rings and the like, and is an improvement over my copending application No. 203,784 filed 5 April 23, 1938.

The main object of the invention is to provide a spring ring such as a piston ring or like article having .the quality of resiliency without such hardness as. would beundesirable in'a sliding bearing element such as a plston ring intended not to produce "substantial wear on'the complementary bearing element such as an engine cylinder wall, and in which the degree of resiliency varies aroundthe length of the annulus.

Among other articles contemplated are hollow pistons such as have a. split skirt portion to which the desired qualities above mentioned are to be imparted, and in which varying resiliency is desired at dlflerent points.

Another object is the provision-of a piston ring or like article having a resilient portion of varying resiliency around the ring and an integral relatively soft portion, the latter having the qualities desired in a bearing intended not to produce substantial wear or scoring of its complementary bearing member.

A specific object is theprovision of a split metallic piston ring having a tempered or hardened portion of high spring quality near and including its inner face, with its thickness greatest opposite the open end, and an integral, normalized or relatively soft portion including the outer or bearing face.

a furtherobject is the provision ofan economical and efficient method of producing piston rings or like articles of the above. kind. having a varying thickness of hardened resilient layer.-

l-Ieretofore, where the varying resilient spring I 40 hatching quality of a split ring was desired, thering was made thicker opposite the split in order to provide increased stiffness and tension at.such point. The. rings thus had eccentric inner and outer walls and thus due to increased radial thickness greater rigidity was imparted to the thicker portion. Such rings required deeper piston grooves,

weakening or causing increases in weight of piston in order to assure thenecessary strength. The present invention presents a simplified economicalsolution of this problem 'in its provision of a ring having concentric inner and outerwalls and yet having greater stiflness opposite the split. The hardened inner layer of varying radial depth integral with the outer soft wearing surface may not only permit of a thinner ring but strength alone E. Somes Serial No.

also permits of the introduction of any degree of 'varying stifiness. An'advantage' of the integrai structure here disclosed is that the outer portion does not have to rely wholly upon its but is' reinforced by the inner integral portion so that the strength of the ring is the combined strength of the whole.

Various other objects and advantages of the in-. vention will be apparent from a perusal of the following specification and the drawing accompanying the same.

In the drawing:

. "Fig. 1 is a perspective'vie'w of a, piston ring embodying the invention.

' Fig. 2 is a side elevation partly in section of a treated cylinder from which .the rings are cut, showing the eccentric coil andhardening. 1 Fig. 3 is a section, on the line 3-3 of Fig. 2. Fig. 4. is a section of .the ring shown in Fig. 1, and illustrating the hard and soft zones.

Fig. 5 is an alternative method involving eccentric quenching and Fig. 615 a diagrammatic showing of the use of an oval coil to produce double eccentricity of 25' hardening as on a piston wall.

Fig. '7 is a section through a modified eccentric ring also eccentrically hardened.

Referring to the drawing in detail and first to Fig. 2, lilrepresents a cylinder of piston ring ma- 7 terial such as any metal or alloy hardenable by heat treatment preferably a, ferrous alloy of a composition such as to have, in the normalized state, the requisitefirmness and softness desirable for the outer portion of the piston ring, and which'upon temperingpr heat treating will assume the quality of resiliency, toughness and other qualities also desirable in a piston ring. This localized diflerence in quality is represented in the drawing by the different densities of wherein the outer lightly hatched portionil indicates the thehardened or heat treated zone. This localized difierence in quality is attained by suitable differential heat treatment of the cylinder blank Ill, preferably through localized heating produced by high frequency electro-magnetic induction followed by quenching, for examplesuch as is disclosed in the copending applications of Howard 50,829,, filed November 21, 1935, for Inside induction heating, and Serial No. 164,320, filed September 1'7, 1937, for .an In- I duction heating treating apparatus. Thus treated, the outer portion including the ex-. ternal surface of the cylinder blank has that rela- V unhardened or normalized zone and the inner densely hatched portion 1 2 is v tive softness and toughness requisite for wearing treating inducing coil may harden two diametripurposes while the interior hardened zone has the cally opposed thicker layers as shown in Fig. 6.

quality of a high degree of resilience. The coil l8 being oval will cause higher current In order to provide gradually increasing stiflconcentrations in the portions l1 and it which ness along one side, a gradually increasing thickupon quenching will produce hardened areas of ness of hardened material is provided by eccengreater cross section than at I! and 20.

tricallv locating the inducing coil as at C with The same ell'ect may be produced by resorting t the cylinder blank l0, so that greater current to an eccentric quenching nozzle, or by providing concentration will be induced in the portion more rapid quenching over portions than others, nearest the inducing coil and hence when sub- 10 thus producing a deeper layer of hardened matesequently quenched, will produce ahardened layrial where rapidly quenched, despite uniform er of greater thickness as shown at I3, and of heating throughout from a concentric coil. Also lesser thickness as shown at I4. eccentric heating as well as eccentric quenching With the cylinder blank brought to the condimay be employed to exaggerate the efiect of one tion thus described, it is cut as by grinding or and thus reduce the extent of heating time or the other suitable method, into separate continuous extent of eccentricity necessary for the coil and rings such as is shown in section in Fig. 4 which quench as when acting above. In Fig. 5, a diaare thereafter split in any suitable manner to grammatic view of an eccentric quenching nozzle form the completed split piston ring as shown in 25 is illustrated. Greater flow of quenching fluid Fig. 1, it being understood that the split is posi as at 26 is provided than at 21, so that greater tioned diametrically opposite the thicker hard-v depth of hardening takes place along'the ring at ened portion. A preferred method of effecting 28 due to faster quenching. The same effect may this splitting of the ring is to grind through part result if the nozzle be eccentricaliy positioned way from one fiat surface toward the other and and the fluid flow uniform in every direction then from the opposite fiat surface, taking a cut from the center of the nozzle. circumferentially offset from the first cut thus It will be understood that the underlying prinproducing the offset lapping .ends as shown in ciple depends on the concentration of currents Fig. 1. along an inner surface area, and where such our- The ring thus formed has the combined qualirents are concentrated, the remainder adjoining ties of varying resiliency desirable for maintain- 30 portion is practically unheated, but where the ing the split ring in expanded condition under currents distribute themselves along the portion Slight but o u f m tension against the walls spaced from the inducing coil, the whole crossof the cylinder in which the ring is to be used. section is heated but to a lower temperature, and

together with the relative softness and toughness while the inner surface becomes most heated, the necessary in a bearing surface intended to make depth of material brought to a hardening temflrm c n t with t y d walls under appreperature is relatively shallow. With the entire ciable pressure without substantial wear or scorcross-section heated, the outer portion does not ing of the cylinder wall. act as a quench, as does the outer portion adjoin- Preferably the material from which the cyllning the portion in which the current is concendrical blank s formed is o e Of the known trated, and' hence this latter portion is subjected other suitable alloys of carbon steel which may to fluid quench as well as the quenching effect of c n a n manganese, P sp rus; sulphur and the adjoining metal which rapidly absorbs heat chromium, and hardenable by heat treatment, fro th heated portion. I the blank, before the hardening heat treatment, whil th invention h b de c ibed as one b in pr p y ormalized in known ma n r to obviating the necessity of providing varying raattain the desired degree of softness and other dially t k rings to bt i varying stifi'ness that qualities of normalized carbon steel. With such is, rings having eccentric internal and external material the inner zone i2 of the finished article u f 11-, l o should be understood that the will be found to consist mainly of martensite and present i v ti n may 'b used in conjunction the outer normalized zone. of sorbite, with an with a ring of non-concentric internal and exterintermediate eccentric zone of troostite, relatively 1 9,] surfac ith t act in conjunction with t n a d s ar y fin h hard t u the varying thickness to provide additional rit a s qui e p y in the normalized gidity orto provide a more uniformly thick soft metal. It will be noted that inasmuch as the wearing th k adjacent the varying t resilient spring portion 12 and the outer bearing ness of the hardened portion. Where such a p r ion II are in l, hey are mutu lly r combined arrangement exists, eccentricity of the forcing so that the bearing portion ll although hardened portion as well as the eccentricity of relativelysoft does not haveto be as thick aswhere th inner and outer surface may both be i Constitutes a Oute Se fupp g n duced since their combined eifects may produce ment separate from an inner expans o g e ethe desired result. Such a ring is illustrated in ment. Thus where desirable, the outer portion ll ection in Fig, 7 and the har ne portion is need besonly thick enough to allow for wear, thus indicated at 30.

permitting substantially the greater portion of While I have herein shown and described a pressure. It is also to be noted that, while for the ring to be formed of a resilient material of specific embodiment of the means and a specific lasting spring quality or low mechanical hysterphase of the method of the invention for the esis, but of varying cross section for more uniform k of disclosure, it is to b understood that the invention is not limited to such specific emthe sake of illustration a definite showing of the bodime i; or phase but; c nt l t 1] u h relative thickness of the two zones at the varying modifications and variants thereof a fall fairly p ts is presented, such show g i made s mp y 7 within the scope of the appended claims.

by way of example; and that in practice the ratio what I 131 i :may be varied to any amount desired. 1. A piston ring having concentric radially in- Pistons of the split variety may likewise be ner and outer faces, said entire inner face and provided with a hardened resilient zone of varythe material adjacent thereto being hardened, ing cross section, and by employing an oval heat 76 said entire outer lace an the material-adjacent thereto being substantially unhardened, the line of demarcation between said hardened and unhardened material extending throughout the ring and being eccentric to said i'aces whereby the radial thickness of said hardened material varies throughout the ring.

2. A metallic piston ring of uniform cross section and having concentric radiall inner and outer faces, said entire inner face and the maened material varies throughout the ring.

3. A split ring of hardenable metal having substantially' circular radially inner and outer faces,

the material adjacent said inner face beinghardened and the material adjacent said outer face being substantially unhardened, the line of demarcation between said hardened and *unhardened material extending throughout the ring and being eccentric to said inner face with the maximum depth of said hardened material positioned substantially opposite the split in the ring.

' '4. A split piston ring having concentric radially inner and outer faces, the material adjacent said inner face being hardened and the material adjacent said outer face being substantial- 1y unhardened, the zone of demarcation between said hardened and unhardened material extendhis throughout the ring and being eccentric to said faces with the maxlmum depth of saidhardened material positioned substantially opposite the split in the ring.

' REN H. FARR. 

